The present invention relates to a color developing agent for a silver halide color photographic photosensitive material and a process for forming an image with this color developing agent. In particular, the present invention relates to a p-phenylenediamine color developing agent capable of forming a color image in combination with a coupler, and a process for forming an image with this color developing agent.
A color photographic image is usually formed by processing a silver halide color photographic photosensitive material as shown below. The photosensitive material is first image-wise exposed and then developed with a developing composition comprising a developing agent. In this step, the silver halide is reduced into silver and the developing agent is oxidized. The thus-prepared oxide of the developing agent is coupled with the coupler to form an image-forming dye corresponding the developed silver. It is well-known that a p-phenylenediamine derivative is used as the color developing agent in order to obtain the color image, taking advantage of the oxidizing power of the exposed silver halide.
Regarding the p-phenylenediamine derivative, for example, alkyl groups at N-position proposed heretofore include N-hydroxyalkyl groups described in U.S. Pat. No. 2,108,243, N-sulfonamidoalkyl groups described in U.S. Pat. Nos. 2,193,015, 2,552,240 and 2,566,271, N-acylaminoalkyl groups described in U.S. Pat. Nos. 2,552,242 and 2,592,363, N-acylalkyl groups described in U.S. Pat. No. 2,374,337, N-alkoxyalkyl groups described in U.S. Pat. No. 2,603,656, Japanese Patent Unexamined Published Application (hereinafter referred to as "J.P. KOKAI") Nos. 47-11534 and 47-11535, Japanese Patent Publication for Opposition Purpose (hereinafter referred to as "J.P. KOKOKU") Nos. 54-16860, 58-14670 and 58-23618, N-sulfoalkyl groups described in British Patent No. 811,679 and N-aralkyl groups described in U.S. Pat. No. 2,716,132. The substituents of the benzene nucleus include, for example, nuclear alkoxyl groups described in U.S. Pat. No. 2,304,953, 2,548,574, 2,552,240 and 2,592,364, nuclear acylaminosulfonamido groups described in U.S. Pat. Nos. 2,350,109 and 2,449,919, nuclear acylaminoalkylsulfonamidoalkyl groups described in U.S. Pat. Nos. 2,552,241, 2,556,271 and 2,592,364, nuclear amino group described in U.S. Pat. Nos. 2,570,116, 2,575,027 and 2,652,331, and nuclear thiosulfonic acid groups described in British Patent No. 872,683. As for the use of compounds analogous to p-phenylenediamine as the color developing agents, tetrahydroquinolines and dihydroindoles are described in U.S. Pat. Nos. 2,196,739 and 2,556,259, N-(p-aminophenyl)hexamethyleneimines are described in U.S. Pat. No. 2,612,500 and 9-aminodurolidines are described in U.S. Pat. No. 2,707,681.
However, the conventional color developing agents have a problem in that the formed dye has yet an insufficient fastness. In particular, the fastness to light is relatively low and, therefore, it is difficult to keep the formed image as it is over a long period of time. Under these conditions, improvement of the storability of the image has eagerly been demanded.
Even though such an improvement has eagerly been demanded, investigations were scarcely made on color developing agents capable of forming a dye of a high fastness. Fastness of images was improved only by various techniques of inhibiting fading of the photosensitive materials.
Various processes are known such as a process wherein a coupler capable of forming a dye of a high fastness is used, a process wherein an ultraviolet ray-absorbing layer comprising an ultraviolet ray-absorber is used, a process wherein various fading inhibitors are used and a process wherein the state of the dye is improved so that the coupler is dispersed in a polymer.
If a color developing agent capable of forming a dye having a quite high fastness is developed, not only the image fastness is improved but also the development of a photosensitive material free from various additives which are essentially unnecessary such as an ultraviolet ray absorber and fading inhibitor is made possible. As a result, the thickness of the photosensitive material can be reduced, the sharpness can be improved and the rapid development is made possible. Further, the cost of the photosensitive material is reduced, since the additives become unnecessary. Thus, great merits can be obtained.
Particularly, photosensitive materials for color prints are usually exposed to a light more often than those for photosensitive materials for taking a picture such as color negative film, and improvement in the fastness of the image is a big theme of investigations. In the photosensitive materials for color printing now available on the market, the fastness of the image is improved by total effects obtained by combination of all the fading-inhibition techniques described above. However, by this fact, the freeness of the formulation of the photosensitive material is restricted. If a color developing agent capable of forming a dye of a quite high fastness is developed, the photosensitive material can be formulated without necessitating any taking of the fastness of the image into consideration and, therefore, freeness of the formulation is increased. For example, a photosensitive material having a remarkably improved coloring property can be thus formulated.